1. Field of the Invention
The present invention relates to a continuously operable seat-reclining device for vehicles, and more particularly to a continuously operable seat-reclining device that can be continuously operated when the back of a seat is angularly moved forward and backward on the basis of the figure of a passenger.
2. Description of the Related Art
A seat-reclining device is a device that is capable of adjusting the angular forward and rearward movement of the back of a seat on the basis of the figure of a driver or a passenger.
In a conventional seat-reclining device, the angular forward and rearward movement of the back of a seat is adjusted by controlling a lock gear, which is operated by a lever, and upper teeth formed at an upper teeth bracket. However, the conventional seat-reclining device has problems in that the angular forward and backward movement of the back of the seat is abruptly adjusted, and therefore the angular forward and backward movement of the back of the seat cannot be finely adjusted. For this reason, continuously operable seat-reclining devices have been increasingly used that are capable of adjusting the angular forward and rearward movement of the back of a seat in a stepless fashion.
Each of the continuously operable seat-reclining devices is operated in the forward or reverse direction in a stepless fashion by means of a lever protruded from one side of the seat or a switch that operates a motor. Each of the continuously operable seat-reclining devices mainly comprises an eccentric cam disposed inside the gears formed at a lower teeth bracket and an upper teeth bracket such that the eccentric cam is rotated to move pitches corresponding to the difference, in the number of teeth, between the lower teeth bracket and the upper teeth bracket, and wedge blocks that control the eccentric cam to prevent a gap while the seat-reclining device is not operated.
Such continuously operable seat-reclining devices have been filed in the name of the applicant of the present application. One example of the continuously operable seat-reclining devices is disclosed in Korean Patent Application No. 10-2003-0025378, wherein a seat-reclining device 30 comprises: an upper teeth bracket 1 having upper teeth 3 formed therein; and a lower teeth bracket 2 having lower teeth 4 formed therein. The upper teeth bracket 1 is securely fixed to a seat back frame, and the lower teeth bracket 2 is securely fixed to a cushion frame.
Between a cam hole 5 formed at the lower teeth bracket 2 and a cam-maintaining ring 6 integrally formed with the upper teeth bracket 1 such that the cam-maintaining ring 6 is protruded from the upper teeth bracket 1 toward the lower teeth bracket 2 is disposed an actuator 10 that is capable of moving the upper teeth bracket 1 relative to the lower teeth bracket 2 so that a reclining operation is substantially carried out.
Around the cam-maintaining ring 6 is disposed a needle bearing 11 to reduce frictional force, and thus improve the reclining operation. Inside the needle bearing 11 is disposed a cam 12 eccentric to the cam-maintaining ring 6.
Inside the cam 12 is formed a wedge groove 15, and in the wedge groove 15 are disposed arch-shaped wedge blocks 16 and 17 to control the movement of the cam 12 such that the cam is eccentric to the cam-maintaining ring 6.
In spring grooves 18, which are formed at the opposite inner ends of the wedge blocks 16 and 17, are disposed wedge springs 19 that increase the distance between the wedge blocks 16 and 17.
An operating surface 13 of the cam 12 is fixed to a shaft 20, which is disposed at the rear of the upper teeth bracket 1. On the outer circumference of the cam 12 is fitted an actuating pin 22 protruded inward from the inside surface of a coupling 21, to which a driving unit is coupled.
In the above-described continuously operable seat-reclining device for vehicles, the cam is maintained by means of the needle bearing. As a result, the continuously operable seat-reclining device for vehicles is affected by vibration generated when the continuously operable seat-reclining device for vehicles is operated or the continuously operable seat-reclining device for vehicles is mounted in the vehicle. Consequently, the cam is not stably maintained.
Especially, an actuating force transmitted through the shaft is applied to the small-sized actuating pin protruded from the coupling, and the cam is moved in the forward and reverse directions by means of the actuating pin. Consequently, serious actuating load is generated at the coupling.
When the above-mentioned actuating load is generated, the actuating force of the shaft is not uniformly transmitted to the coupling. As a result, the shaft is eccentric to one side such that a great amount of the force is transmitted to the actuating pin. Consequently, friction is caused between the shaft and the cam-maintaining ring, by which the actuating load is generated at the entirety of the shaft.
In the above-described continuously operable seat-reclining device for vehicles, the needle bearing is affected by vibration, the actuating force is not satisfactorily transmitted by means of the shaft, and the seat-reclining device is not smoothly operated due to the actuating load. Also, the operation of the continuously operable seat-reclining device is deteriorated as time goes by.